A Graphical User Interface (GUI) is a program interface that takes advantage of a computer's graphics capabilities to make an application easier to use. GUIs can free a user from learning complex command languages. A typical GUI includes a pointer controlled by a pointing device, icons, a desktop area, windows and menus.
A pointer is a symbol that appears on the display screen and that a user moves to select objects and commands. Usually, the pointer appears as a small angled arrow, although different applications may incorporate different pointers. For example, many text-processing applications use a pointer that is shaped like a capital I. The pointer is controlled by way of a pointing device such as a mouse or trackball, which enables the user to select and manipulate objects on the display screen.
Icons are small pictures that represent commands, files, or windows. By moving the pointer to the icon and pressing a mouse button, the user can execute a command or convert the icon into a window. The user can also move the icons around the display screen. The area on the display screen where icons are grouped is often referred to as the desktop. The icons are intended to represent real objects on a real desktop.
A user can divide the display screen into different areas called windows. In each window, a user can run a different program or display a different file. Typically a user can move windows around the display screen, and change their shape and size at will.
Most applications now have a menu-driven component. A menu comprises a graphical list of operations (menu elements) a user can perform. Most graphical user interfaces let a user execute commands by selecting a choice from a menu. A user can choose an item from the menu by highlighting it and then pressing the Enter or Return key, or by simply pointing to the item with a mouse and clicking one of the mouse buttons.
In addition to their visual components, GUIs also make it easier to move data from one application to another. A GUI includes standard formats for representing text and graphics. Because the formats are well-defined, different programs that run under a common GUI can share data. This makes it possible, for example, to copy a graph created by a spreadsheet program into a document created by a word processor.
There are several different types of menus. One type is known as a pop-up menu. A pop-up menu appears temporarily when a mouse button is clicked on a selection. Once you make a selection from a pop-up menu, the menu usually disappears. A pull-down menu is a special type of pop-up menu that appears directly beneath the command selected by the user. A cascading menu is a submenu that opens when a user selects a choice from another menu.
Another type of menu is known as a moving-bar menu. In a moving bar menu, options are highlighted by a bar that a user can move from one item to another. Most menus are moving-bar menus. A menu bar is a menu arranged horizontally. Each menu option is generally associated with another pull-down menu that appears when a user makes a selection. A tear-off menu is a pop-up menu that a user can move around the screen like a window.